Method of manufacturing a CPP structure with enhanced GMR ratio

ABSTRACT

A CPP-GMR spin valve having a CoFe/NiFe composite free layer is disclosed in which Fe content of the CoFe layer ranges from 20 to 70 atomic % and Ni content in the NiFe layer varies, from 85 to 100 atomic % to maintain low Hc and λ s  values. A small positive magnetostriction value in a Co 75 Fe 25  layer is used to offset a negative magnetostriction value in a Ni 90 Fe 10 layer. The CoFe layer is deposited on a sensor stack in which a seed layer, AFM layer, pinned layer, and non-magnetic spacer layer are sequentially formed on a substrate. After a NiFe layer and capping layer are sequentially deposited on the CoFe layer, the sensor stack is patterned to give a sensor element with top and bottom surfaces and a sidewall connecting the top and bottom surfaces. Thereafter, a dielectric layer is formed adjacent to the sidewalls.

This is a Divisional application of U.S. patent application Ser. No.11/180,808, filed on Jul. 13, 2005 that has matured into U.S. Pat. No.7,918,014, which is herein incorporated by reference in its entirety,and assigned to a common assignee.

RELATED PATENT APPLICATIONS

This application is related to the following: U.S. Pat. No. 7,256,971;and U.S. Pat. No. 7,331,100; both assigned to a common assignee.

FIELD OF THE INVENTION

The invention relates to an improved free layer for use in a giantmagnetoresistive (GMR) sensor in a current perpendicular to plane (CPP)magnetic read head and in particular to a composite free layer thatimproves the magnetoresistance (MR) ratio while exhibiting lowcoercivity and negligible magnetostriction.

BACKGROUND OF THE INVENTION

A magnetic disk drive includes circular data tracks on a rotatingmagnetic disk and read and write heads that may form a merged headattached to a slider on a positioning arm. During a read or writeoperation, the merged head is suspended over the magnetic disk on an airbearing surface (ABS). The sensor in a read head is a critical componentsince it is used to detect magnetic field signals by a resistancechange. There is a magnetoresistance effect produced by spin valvemagnetoresistance (SVMR) or giant magnetoresistance (GMR) which is basedon a configuration in which two ferromagnetic layers are separated by anon-magnetic conductive layer in the sensor stack. One of theferromagnetic layers is a pinned layer in which the magnetizationdirection is fixed by exchange coupling with an adjacentanti-ferromagnetic (AFM) or pinning layer. The second ferromagneticlayer is a free layer in which the magnetization vector can rotate inresponse to external magnetic fields. The rotation of magnetization inthe free layer relative to the fixed layer magnetization generates aresistance change that is detected as a voltage change when a sensecurrent is passed through the structure. In a CPP configuration, a sensecurrent is passed through the sensor in a direction perpendicular to thelayers in the stack. Alternatively, there is a current-in-plane (CIP)configuration where the sense current passes through the sensor in adirection parallel to the planes of the layers in the sensor stack.

Ultra-high density (over 100 Gb/in²) recording requires a highlysensitive read head. To meet this requirement, the CPP configuration isa stronger candidate than the CIP configuration which has been used inrecent hard disk drives (HDDs). The CPP configuration is more desirablefor ultra-high density applications because a stronger output signal isachieved as the sensor size decreases, and the MR ratio is higher for aCPP configuration. Furthermore, in U.S. Pat. No. 5,627,704, a GMR-CPPtransducer is described that has a plurality of GMR structures which areconnected serially to provide a larger output signal than can beobtained with a single GMR stack.

In the CPP GMR head structure, a bottom synthetic spin valve film stackis generally employed for biasing reasons as opposed to a top spin valvewhere the free layer is below the spacer and the pinned layer is abovethe copper spacer. Additionally, a CoFe/NiFe composite free layer isconventionally used following the tradition of CIP GMR improvements. Animportant characteristic of a GMR head is the MR ratio which is dR/Rwhere dR is the change in resistance of the spin valve sensor and R isthe resistance of the spin valve sensor before the change. A higher MRratio is desired for improved sensitivity in the device and this resultis achieved when electrons in the sense current spend more time withinthe magnetically active layers of the sensor. Interfacial scatteringwhich is the specular reflection of electrons at the interfaces betweenlayers in the sensor stack can improve the MR ratio and increasesensitivity.

Toshiba has shown (Ref. 3) that for a synthetic anti-parallel (SyAP)pinned layer configuration, laminating the CoFe AP1 layers with thin Culayers can improve the MR ratio in CPP GMR heads. The resulting CPP-GMRbottom spin valve is represented by seed/AFM/pinned/spacer/free/capwhere seed is a seed layer, the spacer is a copper layer, the free layeris a CoFe/NiFe composite, and the pinned layer has an [AP2/coupling/AP1]SyAP configuration in which Ru is the coupling layer and the AP1 layeris a [CoFe_Cu] laminated layer.

U.S. Pat. No. 5,715,121 discloses a further means of CPP-GMR improvementby inserting a confining current path (CCP) layer in the copper spacerby segregating metal path and oxide formation. Moreover, a soft magneticfilm (free layer) is described that is Ni-rich and includes Co such asNi_(0.80)CO_(0.15)Fe_(0.05) and Ni_(0.68)Co_(0.20)Fe_(0.12) or has ahigh Co content as in CO_(0.9)Fe_(0.1) and CO_(0.7)Ni_(0.1)Fe_(0.2).

In a CPP operation mode, a tunnel magnetoresistive (TMR) head is anothercandidate for realizing high sensitivity. In this design, thenon-magnetic conductive layer between the pinned layer and free layer inthe GMR stack is replaced by an insulating layer such as AlO_(x). Whenthe magnetoresistive element is a tunneling magnetic junction (TMJ), thetunneling (insulating) layer may be thinned to give a very low RA (<5ohms-μm²).

A CPP-GMR head is generally preferred over a TMR head design forultra-high density recording because the former has lower impedance.However, the resistance (RA) in a conventional single spin valve is toosmall (<100 mohm-μm²) and the MR ratio of a CPP head may be very low(<5%). Additionally, the output voltage which is related to theresistance change is unacceptably low for many CPP-GMR configurations.One way to increase the resistance change is to optimize the materialsand structure of the CPP-GMR head.

Desirable properties for the free layer in a magnetoresistive elementinclude low coercivity (magnetic softness) of <100e and a lowmagnetostriction (λ_(s)) on the order of 1×E-8 to about 5×10E-6 toreduce stress induced anisotropy. A trend in the industry is to employhigh spin polarization materials such as CoFe in which the atomic % ofFe is >20%, or NiFe in which the atomic % of Fe is >50%, or[(CoFe)_(0.8)B_(0.2)] with ≧25 atomic % Fe in the CoFe composition inorder to produce a higher MR ratio. However, higher spin polarization ina ferromagnetic layer is normally associated with a high saturationmagnetization (Ms) that leads to unacceptably high (λ_(s)) and Hcvalues. A composite free layer with a Co₉₀Fe₁₀/Ni_(82.5)Fe_(17.5)configuration is commonly used in CPP-GMR heads due to its small Hc(˜50e) and low λ_(s) of ˜2×10E-6 but its dR/R ratio is less than 10% andis not large enough for advanced applications. Therefore, an improvedmagnetoresistive element is needed that has a high MR (dR/R) ratio of atleast 10%, low coercivity, and a low λ_(s) value less than about5×10E-6.

U.S. Pat. No. 6,888,707 discloses an improved free layer comprised of avery thin CoFe/NiFe composite layer. The Fe content in the CoFe layer isabout 10 atomic % and the Fe content in the NiFe layer is about 19%which provides low Hc and λs values. However, the dR/R ratio is notlarge enough for ultra high density recording purposes.

In U.S. Pat. No. 6,519,124 and U.S. Pat. No. 6,529,353, a NiFe/CoFe freelayer is mentioned but the atomic % of Fe in each layer is notspecified. Therefore, the patents do not teach how to resolve the highλs that would result from a high spin polarization CoFe component in thefree layer.

U.S. Patent Application Publications 2004/0047190 and 2003/0197505describe a Ni rich NiCoFe free layer wherein the Ni content is 60 to 90atomic %. This layer is not used in combination with a CoFe lower layerand is designed as a “soft” magnetic layer.

In U.S. Patent Application Publication 2004/0091743, a composite freelayer comprised of an upper NiFe(13.5%) layer and a lower CoFe(16%)layer is disclosed. The free layer is optimized for a slightly negativemagnetostriction and does not take into account dR/R which is expectedto be low because of the low Fe atomic %.

SUMMARY OF THE INVENTION

One objective of the present invention is to provide a higher MR ratioof at least 10% in a CPP-GMR spin valve structure while maintaining alow coercivity (<5 Oe) and a low λ_(s) of less than about 5×10E-6.

A further objective of the present invention is to provide a method offorming the improved CPP-GMR spin valve head in accordance with thefirst objective.

These objectives are achieved in one embodiment in which a substrate isprovided that may be a first magnetic shield (S1) in a magnetic readhead. A sequence of layers is then deposited on the substrate to form asensor stack with a CPP-GMR configuration that is preferably a bottomspin valve type. In the exemplary embodiment, a seed layer, AFM layer,pinned layer, spacer, free layer, and cap layer are sequentially formedon the substrate. The pinned layer may have a SyAP (AP2/coupling/AP1)configuration in which the AP1 layer is made of a laminated film of CoFeand Cu layers and the coupling layer is a Ru layer. A copper spacer onthe AP1 layer may be advantageously comprised of a middle CCP layer madeof oxidized AlCu. A key feature is that the free layer is a compositelayer comprised of a higher content (v≧20 atomic %) Fe_(v)Co_((100-v))layer where v is from 20 to 70 atomic % and a Ni rich (w≧85 atomic %)Ni_(w)Fe_((100-w)) layer. A higher MR ratio is attributed to the higherFe content in the FeCo layer while Hc and λ_(s) are minimized by the Nirich NiFe layer.

The layers are sputter deposited using Ar gas in a sputtering systemthat is preferably equipped with an ultra-high vacuum. Oxide formationand segregated metal path definition in the AlCu CCP layer are achievedby following RF-PIT and RF-IAO processes that can be performed in aseparate chamber in the sputter system. After the cap layer isdeposited, the CPP GMR stack is patterned by a conventional method toform a CPP GMR sensor having a top surface with sidewalls. A well knownfabrication sequence is then followed that includes forming aninsulating layer adjacent to both sidewalls and a second magnetic shield(S2) on the cap layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a CPP-GMR spin valve structureaccording to one embodiment of the present invention.

FIG. 2 is a cross-sectional view of a CPP-GMR read head showing the spinvalve structure of the present invention formed between a first shieldand a second shield.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is a CPP-GMR spin valve structure for use as asensor in a read head of a magnetic recording device and a method formaking the same. The read head may be part of a merged read/write head.The spin valve structure is especially suited for an ultra-high magneticrecording device wherein the recording density is greater than about 100Gbits/in². The drawings are provided by way of example and are notintended to limit the scope of the invention. Although a bottom spinvalve structure is shown in the exemplary embodiments, those skilled inthe art will appreciate that the novel composite free layer of thepresent invention can also be incorporated in a top spin valve or inmultilayer spin valves. Moreover, the invention encompasses TMR sensorsor other magnetic devices that are based on a magnetoresistance effectand include a ferromagnetic free layer.

A first embodiment is set forth in FIG. 1 in which a GMR-CPP or TMRsensor comprised of a bottom spin valve structure is illustrated. Theview in FIG. 1 is from a cross-section along an (air bearing surface)ABS plane in the read head. The inventors have unexpectedly found thatthe Fe content in a FeCo layer of a FeCo/NiFe composite free layer in aCPP GMR or TMR spin valve structure may be increased substantially to≧20 atomic % without resulting in unacceptably high magnetostriction byincreasing the Ni content in the NiFe layer to ≧85 atomic %.

A novel spin valve structure 1 will be described first and then a methodof forming the stack of layers in the spin valve structure will beprovided. Referring to FIG. 1, a substrate 10 is shown that is typicallya first magnetic shield (S1) in a read head. For example, the substrate10 may be comprised of a 2 micron thick layer of an electroplatedpermalloy. There is a seed layer 11 that may be comprised of a lower Talayer (not shown) having a thickness from 10 to 60 Angstroms andpreferably about 50 Angstroms thick, and an upper Ru layer having athickness about 5 to 40 Angstroms thick and preferably 20 Angstromsthick formed on the substrate 10. The seed layer 11 promotes a smoothand uniform crystal structure in the overlying layers that enhances theMR ratio in the spin valve structure 1.

An AFM layer 12 is formed on the seed layer 11 and is preferablycomprised of IrMn having a composition of about 18 to 22 atomic % Ir anda thickness of about 50 to 75 Angstroms. Alternatively, the AFM layer 12may be made of MnPt having a composition between about 55 to 65 atomic %manganese and with a thickness of about 125 to 175 Angstroms. Thoseskilled in the art will appreciate that other materials such as NiMn,OsMn, RuMn, RhMn, PdMn, RuRhMn, or PtPdMn may also be employed as theAFM layer 12 which is used to pin the magnetization direction in anoverlying ferromagnetic (pinned) layer 20.

In one embodiment, a synthetic anti-parallel (SyAP) pinned layer 20 isformed on the AFM layer 12 and is preferably comprised of an AP2/Ru/AP1configuration. The AP2 layer 13 is preferably comprised of CoFe with acomposition of about 75 to 90 atomic % cobalt and a thickness of about20 to 50 Angstroms. The magnetic moment of the AP2 layer 13 is pinned ina direction anti-parallel to the magnetic moment of the AP1 layer. Forexample, the AP2 layer may have a magnetic moment oriented along the“+x” direction while the AP1 layer has a magnetic moment in the “−x”direction. The AP2 layer 13 is generally slightly thinner than the AP1layer to produce a small net magnetic moment for the pinned layer 20.Exchange coupling between the AP2 layer 13 and the AP1 layer isfacilitated by a coupling layer 14 that is preferably comprised of Ruwith a thickness of about 7.5 Angstroms. Optionally, Rh or Ir may beemployed as the coupling layer 14.

Preferably, the AP1 layer is a composite with a [CoFe/Cu]_(n)/CoFeconfiguration where n=2 or 3. In the exemplary embodiment, n=2 and theAP1 layer is comprised of CoFe layer 15, Cu layer 16, CoFe layer 17, Culayer 18, and CoFe layer 19 that are formed sequentially on the couplinglayer 14. The Cu layers 16, 18 are from 0.5 to 4 Angstroms thick andpreferably 2 Angstroms thick while the CoFe layers 15, 17, 19 each havea CoFe composition with a Fe content of about 70 atomic % and athickness between about 7 and 15 Angstroms, and preferably 12 Angstroms.The use of a laminated AP1 layer to improve CPP-GMR properties wasdiscussed previously. Note that each of the CoFe layers 15, 17, 19 has amagnetic moment in the “−x” direction when the AP1 layer has a magneticmoment along the “−x” axis.

In a preferred embodiment, a non-magnetic spacer 24 is formed on theSyAP pinned layer 20. When the non-magnetic spacer 24 is made of Cu asin a CPP-GMR sensor, an oxygen surfactant layer (not shown) may beformed on the copper layer according to a method described in Headwaypatent application HT03-009 which is herein incorporated by reference inits entirety. The oxygen surfactant layer is less than about 1 atomiclayer in thickness and is used to improve lattice matching between thecopper layer and an overlying magnetic layer which in this case is thefree layer 27. In other words, the oxygen surfactant layer relievesstress in the spin valve structure 1 and is also used to grow a smoothoverlying magnetic layer. Alternatively, for a TMR sensor, thenon-magnetic spacer 24 is referred to as a tunnel barrier layer and iscomprised of a dielectric material such as AlOx.

In the exemplary embodiment, the non-magnetic spacer 24 is made of Cuwith a thickness of about 20 to 50 Angstroms and is comprised of aconfining current path (CCP) layer 22 formed between a lower copperlayer 21 and an upper copper layer 23. As mentioned previously, a CCPlayer may be employed in a CPP-GMR spin valve structure to improveperformance. In one aspect, the lower Cu layer 21 is about 2 to 8Angstroms thick and preferably 5.2 Angstroms thick, and the upper Culayer 23 has a thickness between 2 and 6 Angstroms and is preferably 3Angstroms thick. The CCP layer 22 may be made of AlCu that has beenpartially oxidized by a process described in a later section. The CCPlayer 22 has a thickness from 6 to 10 Angstroms and is preferably madefrom an AlCu layer having a thickness of about 8.5 Angstroms and an Alcontent of about 90 atomic %.

A key feature of the present invention is the free layer 27 formed onthe non-magnetic spacer 24. The free layer 27 is a composite having alower CoFe layer 25 about 5 to 30 Angstroms thick and an upper NiFelayer 26 with a thickness of from 10 to 60 Angstroms. In particular, thelower CoFe layer 25 has a composition represented by Fe_(v)Co_((100-v))wherein v ranges from about 20 to 70 atomic % and the upper NiFe layer26 has a composition represented by Ni_(w)Fe_((100-w)) wherein w rangesfrom 85 to 100 atomic %. In the prior art, the Fe content in a CoFe freelayer has been kept below 20 atomic % because of a concern aboutunacceptably high λ_(s) and Hc values associated with a Fe content of≧20 atomic %, and especially with a Fe content above 35 atomic %. TheNiFe component of prior art free layers has a Ni content of <85 atomic %in order to optimize the Fe content since it is well known that a higherFe concentration in a free layer improves the MR ratio of a spin valve.The inventors have found that the major contribution towards a higher MRratio comes from increasing the Fe content to ≧20 atomic % in the lowerFeCo layer 25. By raising the Ni content to ≧85 atomic % in the NiFelayer 26 which is magnetically coupled to the lower FeCo layer 25, theλ_(s) and Hc values for the free layer 27 are maintained withinacceptable limits without significantly affecting the MR ratio gain fromthe FeCo component.

In a preferred embodiment, the FeCo layer 25 has a Fe₂₅Co₇₅ compositionand a thickness of about 20 Angstroms while the NiFe layer 26 has aNi₉₀Fe₁₀ composition and a thickness of about 28 Angstroms. Theaforementioned Fe₂₅CO₇₅ and Ni₉₀Fe₁₀ layers are advantageously selectedsince the magnetic moment of Ni₉₀Fe₁₀ is very small and itsmagnetostriction is negative while the magnetic moment of Fe₂₅CO₇₅ isonly slightly larger than that of Fe₁₀CO₉₀ and its magnetostriction isslightly positive. As a result, a composite free layer 27 comprised ofFe₂₅Co₇₅/Ni₉₀Fe₁₀ will allow the maximum contribution from the bulkscattering of the Fe₂₅CO₇₅ layer while maintaining free layer softnessand small magnetostriction. Thus, the overall performance of the spinvalve structure 1 has been enhanced relative to a similar spin valveconfiguration with a standard Fe₁₀CO₉₀/Ni_(82.5)Fe_(17.5) free layerbecause of a larger MR ratio while maintaining acceptable Hc and λ_(s)values.

The magnetic moment of the free layer 27 is preferably aligned along they-axis in a quiescent state and can rotate to a magnetic direction alongthe x-axis under an appropriately sized applied magnetic field such aswhen the spin valve structure 1 is moved along the ABS plane over amagnetic disk in the z-direction.

The top layer in the spin valve stack is a cap layer 28 that in oneembodiment has a Cu/Ru/Ta/Ru configuration in which the Cu layer has athickness of 10 to 40 Angstroms, the lower Ru layer has a thickness of10 to 30 Angstroms, the Ta layer is 40 to 80 Angstroms thick, and theupper Ru layer is 10 to 30 Angstroms thick. Optionally, other cap layermaterials used in the art may be employed as the cap layer 28.

Table 1 lists the properties of a CPP-GMR spin valve (wafer #2)according to the present invention compared with a CPP-GMR spin valve(wafer #1) previously made by the inventors. The spin valve structuresdiffer only in the composition of the free layer. Note that the numbers(excluding subscripts) refer to thickness in Angstroms for the seedlayer (Ta50/Ru20), AFM layer (IrMn70), SyAP pinned layer[Fe₂₅CO₇₅46/Ru7.5/(Fe₇₀CO₃₀12/Cu2)₂/Fe₇₀Co₃₀12], copper spacer with CCPlayer (Cu5.2/AlCu8.5/RF PIT/RFIAO/Cu3), and cap layer(Cu30/Ru10/Ta60/Ru10). RF-PIT and RF-IAO indicate processes used totreat the AlCu layer to form a CCP layer within the copper spacer. TheRF PIT process in Table 1 involves etching the AlCu layer with a RFpower of 20 Watts and an Ar flow rate of 50 standard cubic centimetersper second (sccm) for 40 seconds. The RF-IAO process comprises a RFpower of 27 Watts, an Ar flow rate of 50 sccm and an O₂ flow rate of 0.8sccm for a period of 30 seconds. The free layer in wafer #1 has a 10Angstrom thick lower Fe₂₅CO₇₅ layer and a 35 Angstrom thick upperNi_(82.5)Fe_(17.5) layer while the free layer in wafer #2 has a 20Angstrom thick lower Fe₂₅CO₇₅ layer and a 28 Angstrom thick upperNi₉₀Fe₁₀ layer.

The advantages of the present invention are summarized by the results inTable 1. Wafer #2 shows an improvement over wafer #1 in that dR/R hasincreased from 8.6% to 10% (a 16% relative increase) andmagnetostriction has decreased to 7.0×10 E-8 while RA and Hc values aremaintained at an acceptable level. It should be understood that if astandard CO₉₀Fe₁₀ layer is employed rather than the CO₇₅Fe₂₅ layer inthe free layer of wafer #1, the dR/R would be less than 8.6%. In otherwords, both a higher Fe content in the lower FeCo layer and a higher Nicontent in the NiFe layer of the free layer contribute to thecombination of high dR/R, low λs, and low Hc which has not been achievedpreviously.

TABLE 1 CCP-GMR properties with various free layer configurations WaferHc ID Spin Valve Configuration RA dR/R (Oe) λs #1Ta50Ru20/IrMn70/Fe₂₅Co₇₅46/ 0.25  8.6% 4.6 2.3E−06 Ru7.5/[Fe₇₀Co₃₀12/Cu2]₂Fe₇₀Co₃₀12/Cu5.2/AlCu 8.5/RF PIT/RFIAO/Cu3/Co₇₅Fe₂₅10/Ni_(82.5)Fe_(17.5)35/ Cu30/Ru10/Ta60/Ru10 #2Ta50Ru20/IrMn70/Fe₂₅Co₇₅46/ 0.26 10.0% 4.9 7.0E−08 Ru7.5/[Fe₇₀Co₃₀12/Cu2]₂Fe₇₀Co₃₀12/Cu5.2/AlCu 8.5/RF PIT/RFIAO/Cu3/Co₇₅Fe₂₅20/Ni₉₀Fe₁₀28/Cu30/ Ru10/Ta60/Ru10

Referring to FIG. 2, a method of fabricating a magnetic read head 40that includes the spin valve structure 1 from FIG. 1 will now bedescribed. A substrate 10 is provided as mentioned previously and may bea first magnetic shield (S1) formed by a conventional method in the readhead 40. The spin valve stack described previously is laid down by aprocess in which the seed layer 11, AFM layer 12, pinned layer 20,non-magnetic spacer 24, free layer 27, and cap layer 28 are sequentiallyformed on the substrate 10. A DC magnetron sputter system such as oneavailable from Anelva may be employed that is capable of a base pressureof at least 1×10⁻⁸ torr and preferably less than 5×10⁻⁹ torr which isabout 1 order of magnitude lower than a CVC system used in the art. Alower base pressure allows films to be sputter deposited with higheruniformity and reproducibility. It should be understood that a sputterchamber may have multiple targets which are low pressure dischargecathodes. The sputter gas is preferably Ar. All of the sputter depositedfilms may be laid down in the same sputter chamber or in differentsputter chambers within the same mainframe.

In an embodiment where the non-magnetic spacer 24 is comprised of alower Cu layer 21, a CCP layer 22, and an upper Cu layer 23 (FIG. 1),the CCP layer may be formed by depositing an AICu layer about 6 to 10Angstroms thick on the lower Cu layer followed in succession by a RF(plasma or ion treatment) PIT process and a RF-IAO process to form apartially oxidized AICu layer. The RF PIT and RF-IAO (plasma oxidationor ion assisted oxidation) processes are preferably performed in aseparate chamber within the sputter system and have been previouslydescribed in Headway application HT03-043 which is herein incorporatedby reference in its entirety. The RF PIT process preferably involves alow power plasma etch to remove about 1 to 3 Angstroms of the AlCu layerand may comprise the following conditions: an Ar flow rate of about 50sccm and a RF power level of 17 to 20 Watts for about 20 to 60 seconds.During the RF-IAO process, the AlCu layer is subjected to plasmaoxidation which converts the AlCu layer into CCP layer 22 that isessentially a porous aluminum oxide layer whose pores are filled withCu. The RF-IAO process typically comprises the following conditions: anAr flow rate of about 30-50 sccm, an O₂ flow rate of 0.3 to 1 sccm, anda RF power level of 20 to 30 W for about 15 to 45 seconds. Subsequently,the upper Cu layer 23 is sputter deposited on the CCP layer 22 followedby the sequential deposition of the free layer 27 and cap layer 28 onthe upper Cu layer.

Optionally, for a read head 40 that is based on TMR spin valve structure1, the non-magnetic spacer (tunnel barrier) 24 is prepared by firstdepositing an Al layer or the like about 5 to 6 Angstroms thick on thepinned layer 20 and then oxidizing with a natural oxidation or radicaloxidation to form an oxide layer such as AlOx which has a stoichiometryclose to that of Al₂O₃.

After all of the layers in the spin valve stack are laid down on thesubstrate 10, the spin valve stack is patterned and etched by a wellknown process that employs a photoresist layer (not shown) and an ionbeam etch (IBE) method, for example. Following the etch step, a spinvalve structure having a top surface 28 a and sidewalls 29 is defined.An insulating layer 30 is typically deposited to a depth that covers thesidewalls 29. There may also be a biasing layer (not shown) that isformed within the insulating layer 30 proximate to each side of the spinvalve structure to provide longitudinal biasing to the free layer asappreciated by those skilled in the art. Thereafter, the photoresistlayer is removed by a lift-off process and the insulating layer 30 maybe smoothed by a planarization technique such as a chemical mechanicalpolish (CMP) method to become coplanar with the top surface 28 a.

The spin valve structure 1 may be annealed in a magnetic field of about8000 and 12000 oersted at a temperature between about 250° C. and 300°C. for a period of 2 to 5 hours. The remainder of the read head 40 maythen be fabricated by a conventional process. For example, a secondmagnetic shield 31 may be formed on the top surface 28 a and over theinsulating layer 30. Those skilled in the art will appreciate that in aCPP spin valve structure, the second magnetic shield layer (S2) is alsoused as the top conductor lead layer.

While this invention has been particularly shown and described withreference to, the preferred embodiment thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade without departing from the spirit and scope of this invention.

We claim:
 1. A method for fabricating a spin valve structure for use asa sensor in a magnetic read head, comprising: (a) providing a substrateand forming thereon a spin valve stack comprised of: (1) ananti-ferromagnetic (AFM) layer that pins an adjacent pinned layer: (2)the pinned layer: (3) a free layer that is a composite film comprised ofa lower Fe_(v)Co(_(100-v))layer in which v is from about 20 to 70 atomic%, and an upper Ni_(w)Fe(_(100-w)) layer wherein w is from 85 to 100atomic %; and (4) a non-magnetic spacer formed between the pinned layerand free layer wherein the non-magnetic spacer is comprised of Cu andhas a confining current path (CCP) layer formed therein between a lowerCu layer and an upper copper layer, said CCP layer is made of AICu thathas been partially oxidized; and (b) patterning said spin valve stack toform a spin valve structure having sidewalls and a top surface, saidsidewalls are substantially planar along the entire free layer.
 2. Themethod of claim 1 wherein the pinned layer is comprised of anAP2/coupling/AP1 configuration in which the AP2 layer is a CoFe layerhaving an Fe content of about 25 atomic , the coupling layer is Ru, andthe AP1 layer is a lamination of CoFe layers having an Fe content ofabout 70 atomic % and Cu layers represented by the composition(CoFe/Cu)_(n)/CoFe in which n =2 or
 3. 3. The method of claim 1, whereinthe CCP layer is formed by depositing an AlCu layer on the lower Culayer followed by a plasma or ion treatment (RF PIT) process thatremoves about 1 to 3 Angstroms of the AlCu layer and then a plasmaoxidation or ion assisted oxidation (RF-IAO) process that oxidizes saidAlCu layer to form a porous aluminum oxide layer having pores that arefilled with Cu.
 4. The method of claim 1 wherein the spin valve stack isformed by successively depositing a seed layer, the AFM layer, thepinned layer, the spacer, the free layer, and a cap layer on saidsubstrate and the subsequent patterning process forms a bottom spinvalve structure.
 5. The method of claim 1 further comprised of formingan insulating layer that adjoins the sidewalls of the spin valvestructure, and forming a biasing layer within the insulating layer, saidbiasing layer provides longitudinal biasing to the free layer in thespin valve structure.
 6. The method of claim 1 further comprised ofannealing the spin valve structure with a magnetic field of about 8000and 12000 Oersted at a temperature between about 250° C. and 300° C. fora period of about 2 to 5 hours.
 7. The method of claim 1 wherein thelayer has a Fe_(v)Co (_(100-v) ) layer has a Fe ₂₅Co₇₅composition and athickness of about 20 Angstroms while the Ni_(w)Fe(_(100-w)) layer has aNi₉₀Fe₁₀ composition and a thickness of about 28 Angstroms.
 8. A methodfor fabricating a spin valve structure for use as a sensor in a magneticread head, comprising: (a) providing a substrate and forming thereon aspin valve stack comprised of: (1) an anti-ferromagnetic (AFM) layerthat pins an adjacent pinned layer; (2) the pinned layer that iscomprised of an AP2/coupling/AP1 configuration in which the AP2 layer isa CoFe layer having an Fe content of about 25 atomic %, the couplinglayer is Ru, and the AP1 layer is a lamination of CoFe layers having anFe content of about 70 atomic %; (3) a free layer that is a compositefilm comprised of a lower Fe_(v)Co(_(100-v)) layer in which v is fromabout 20 to 70 atomic %, and an upper Ni_(w)Fe(_(100-w)) layer wherein wis from 85 to 100 atomic %; and (4) a non-magnetic spacer formed betweenthe pinned layer and free layer wherein the non-magnetic spacer is atunnel barrier layer that is comprised of a dielectric material; and (b)patterning said spin valve stack to form a spin valve structure havingsidewalls and a top surface, said sidewalls are substantially planaralong the entire free layer.
 9. A method for fabricating a spin valvestructure for use as a sensor in a magnetic read head, comprising: (a)providing a substrate and forming thereon a spin valve stack comprisedof: (1) an anti-ferromagnetic (AFM) layer that pins an adjacent pinnedlayer; (2) the pinned layer that is comprised of an AP2/coupling/AP1configuration in which the AP2 layer is a CoFe layer having an Fecontent of about 25 atomic %, the coupling layer is Ru, and the AP1layer is a lamination of CoFe layers having an Fe content of about 70atomic %; (3) a free layer that is a composite film comprised of a lowerFe_(v)Co(_(100-v)) layer in which v is from about 20 to 70 atomic %, andan upper Ni_(w)Fe(_(100-w)) layer wherein w is from 85 to 100 atomic %;and (4) a Cu spacer formed between the pinned layer and free layer; and(b) patterning said spin valve stack to form a spin valve structurehaving sidewalls and a top surface, said sidewalls are substantiallyplanar along the entire free layer.